1. Field of the Invention
The invention relates to flexible heating mats for melting snow and ice on driveways, walkways, including stairs, and roofs.
2. Description of Related Art
Over the years there have been a number of attempts to melt snow and ice accumulations by heating the affected surface. Most past configurations required a permanent installation of the heating element inside the surface, as exemplified by Watanabe in U.S. Pat. No. 5,605,418 and Deschenes in U.S. Pat. No. 4,564,745. These solutions however tend to be expensive, are not readily adaptable to existing surfaces, and maintenance and repair often require destruction and reconstruction of the protected surface.
Several attempts at melting snow and ice accumulations by placing a heater on the surface of the area to be cleared have been made, as discussed below. Bayless et al., U.S. Pat. No. 4,967,057 teaches the use of multiple individual panels to cover varying size areas. The Bayless patent however calls for multiple connections between the separate panels, presenting potential failure points. Additionally the panel may be dislocated or disconnected when driven upon. Bayless also requires a large number of panels to cover large areas and thus is not desirable for installation on driveways. In fact, Bayless discloses that the panels are appropriate to steps and walkways only.
Another attempt by Shields, in U.S. Pat. No. 5,591,365 addresses those concerns by placing the heating element in a flexible lattice form. However, Shields uses a single series resistive element in the form of specialized and expensive heating cables distributed throughout the lattice. The use of a single series heating element prevents field customization of the heater to fit varying length of protected areas, and reduces reliability since a break in any point along the heater will render the whole apparatus inoperative.
Similar patents include U.S. Pat. No. 5,614,292 to Saylor, U.S. Pat. No. 5,003,157 to Hargrove, U.S. Pat. No. 3,806,702 to Spencer, and U.S. Pat. No. 5,637,247 to Flynn, Jr. Patents, such as U.S. Pat. No. 3,900,654 to Stinger have described heater elements allowing trimming to any desired length, comprising a thin, flexible laminated assembly of electrically conductive elastomeric material. U.S. Pat. No. 4,523,085 to Grise teaches flexible sheet film heating elements that comprises current feed electrodes, heretofore referred to as bus bars, disposed in parallel along two sides of the heater film. Multiple resistive ink patterns traversely connect between the bus bars to form an array of parallel connected heater elements. This arrangement allows for field customization of the heater length since the film heater may be cut anywhere between the parallel connected heating elements. However the Grise heater is not durable enough to sustain people or vehicular traffic or prolonged exposure to elements such as ultraviolet light, ozone, sand and chemicals. Additionally when cut, the Grise heater does not offer submersion protection since the bus bars are exposed at the cut end.
All the above, taken individually or in combination do not teach the current invention as claimed. An inexpensive solution to the problem of snow removal by electrical means that is easy to install by untrained personnel, and that may be sold in roll form to allow cutting for any desired length in the field is therefor clearly highly desirable and is presented in the instant invention.